In the computer science field, a “snapshot” is a term that is used to refer to the state of a set of data at a particular point in time. There are many reasons to implement snapshots of different data. For example, it is often desirable to implement snapshots of an entire disk drive. The snapshot of the disk drive may be useful, for example, to permit distribution and/or backup of a consistent disk image across many devices in a given system or computing environment.
Many types of data and storage management systems can be used to implement snapshots. Different types of volume managers and file systems can be used to implement and maintain snapshots. Such storage management systems that may be used to implement snapshots include, for example, logical volume manager in UNIX-based systems.
Many snapshots are “read only” snapshots, in which the snapshot of the data cannot be modified. This allows for very simple management of the snapshot.
A “writable” snapshot is a type of snapshot that permits modifications to the snapshot. The user is provided the writable snapshot in such a way that the user can later perform modifications to that snapshot. For example, consider the situation in which a disk image including an operating system that is provided to a user in the form of a writable snapshot. As the user makes use of the operating system in the writable snapshot, it is likely that changes and modifications will occur to various files in the writable snapshot pertaining to the operating system, such as to files that maintain the system registry.
Once a modification is made to the snapshot, then a new variant of the snapshot is created which differs from the original snapshot. However, it is likely that both the original snapshot and the new variants of the snapshot will need to be maintained in the overall computing system. As more changes are introduced by different entities in the computing system, there will be an extending proliferation of such snapshot variants into the system.
As is evident, writable snapshots are much more complicated to maintain and administer as compared to read-only snapshots. Writable snapshots may also be much more expensive to implement, since the act of copying the data of the original writable snapshot into a new variant of the writable snapshot could end up consuming a significant amount of system resources for the computing system, and incur a significant amount of wait time for the user.
Therefore, there is a need for an efficient approach to implement and maintain writable snapshots.